As optical discs have developed to CDs, DVDs, and Blu-rays with increasing storage capacities, the file systems have been taken over by new generations. To be specific, ISO 9660 was taken over by a file system called UDF (Universal Disk Format) that was defined by OSTA (Optical Storage Technology Association) and was standardized by ISO/TEC and Ecma International (e.g., see Non-Patent Literatures 1 and 2). After that, UDF has been revised several times. UDF 2.50 has been adopted for BD-RE (Ver. 2.0/2.1/3.0) and BD-ROM (Ver. 1.0) and UDF 2.60 has been adopted for BD-R (Ver 1.0) (e.g., see Non-Patent Literatures 3 to 5).
Generally, optical discs on which information is recorded thus are bare discs and the surfaces of the discs are likely to be contaminated or damaged during the manufacturing or use of the optical discs. In the case where defects occur and the management information of a file system is not correctly read, a recorded file cannot be reproduced. Conversely, even if a file body is defectively read, a file can be reproduced simply by correctly reading the management information. Thus in order to read a file regardless of whether the file body is defective or not, file system management areas are recorded at two points in UDF to have a dual management structure. The file system management area contains management information for managing the hierarchical structure of a file system and the recording area of a file body. With this structure, even when one of the management areas is defectively read, a file can be reproduced by reading the other management area (e.g., see Patent Literature 1).
In another known technique, in order to securely perform reproduction when an impact from an external factor causes damage or fingerprints are placed, important file system management areas are not situated on the inner and outer peripheries of a disc but on the inner and intermediate parts that are less subjected to fingerprints and scratches (e.g., see Patent Literature 2).